serve as information for maintenance and repair in the
same way as those in shipboard electronics systems.
Detailed block diagrams of complicated systems that
contain details of signal paths, wave shapes, and so on
are usually called signal flow diagrams.
Wiring Diagrams
Aircraft electronic wiring diagrams fall into two
basic classes: chassis wiring diagrams and interconnect-
ing diagrams. There are many variations of each class,
depending on the application.
Figure 6-20, view A, shows an example of one type
of chassis wiring diagram. This diagram shows the
physical layout of the unit and all component parts
and interconnecting tie points. Each indicated part is
identified by a reference designation number that helps
you use the illustrated parts breakdown (IPB) to deter-
mine value and other data. (Wiring diagrams normally
do not show the values of resistors, capacitors, or other
components.) Since this specific diagram shows
physical layout and dimensioning details for mounting
holes, it could be used as an assembly drawing and as
an installation drawing.
Figure 6-20, view B, shows the reverse side of the
same mounting board, together with the wiring inter-
connections to other components. It does not show the
actual positioning of circuit components, and it shows
wire bundles as single lines with the separate wires
entering at an angle.
The wire identification coding on this diagram con-
sists of a three-part designation. The first part is a
number representing the color code of the wire accord-
ing to Military Specification MIL-W-76B. (Many other
chassis wiring diagrams designate color coding by
abbreviation of the actual colors.) The second part is the
reference part designation number of the item to which
the wire is connected, and the last part is the designation
of the terminal to which connection is made.
Figure 6-20, view C, is not a wiring diagram, but it
illustrates a method commonly used to show some
functional aspect of sealed or special components.
Figure 6-20, view D, illustrates several methods
used to show connections at terminal strips, as
discussed earlier.
Electromechanical Drawings
Electromechanical devices such as synchros,
gyros, accelerometers, autotune systems, an analog
computing elements are quite common in avionics
systems. You need more than an electrical or
electronic drawing to understand these systems
adequately; therefore, we use a combination drawing
called an electromechanical drawing. These drawings
are usually simplified both electrically and mechan-
ically, and show only those items essential to the
operation. Figure 6-21 shows an example of one type
of electromechanical drawing.
Figure 6-21.—Aircraft gyro fluxgate compass, electromechanical drawing.
6-21
